DH.126 Additional Information

Cy-27

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I am first-time poster so apologies for any breaches in the forum etiquette with this post, feel free to shunt it into any category that may be more suitable.

I have recently been looking at the Secret Projects Forum > Research Topics > Designation Systems > De Havilland aircraft thread and saw the entry about the DH-126, a project for 35-50 passenger airliner with two rear mounted turbofans.

I have a de Havilland "Additional Information" document on the DH126 from the summer of 1960 that may be of interest.

It appears to be a development of the DH125 rather than a full blown new design. The document describes the type as "a small turbofan airliner" with a good deal of the aerodynamic and structural details of the DH125. Is basic selling price was estimated as £140,000.

Some interesting details mentioned include:

Proposed turbofans engines:

Bristol Siddeley BS.88
Rolls Royce RB 172/3 (new engine)
de Havilland PS 90
de Havilland PS 92

Weights:
Empty: 11,955 lbs
Operators items (crew & emergency equipment): 758 lbs
Payload: 6,300 lbs
Fuel: 3,387 lbs
Total take-off weight: 22,400 lbs

Civil Applications:
The type has a payload and range graph quoting between 24-30 seats.

"The DH126 will suit the routes of most of the BOAC Associates fairly well namely:
British West Indian Airways
West African Airways (Ghana and Nigeria)
Malayan Airways
Various small airliners

In general, apart from an odd aerodrome such as Jos in West Africa, the aerodrome performance of the DH126 was more than adequate."


Military Applications:
A navigational trainer version is also described and illustrated with 2 crew, 1 instructor, 2 pupils, 4 passengers plus navigational equipment as a potential Valetta replacement.

An electronic training configuration (2 crew, 1 instructor, 4 pupils, 4 passengers) is also shown as a drawing.

The documents conclusion states "the DH126 can meet the Varsity and VIP Valetta replacement requirements....it would be very suitable as a replacement for the Queen's flight Herons"

I don't know the DH125 Dominie configuration for the RAF - is it similar to the details above?

Summary
The document also compares the DH126 with the DH123 project in its payload/range, operating costs, work capacity and speed graphs.

From the drawings the cabin appears very similar in size to the DH125. Do you think this could be a different use of the designation to the one listed in Hesham's original post.

I hope this is of some interest.
 

Jos Heyman

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Here is a drawing of the DH-126. I think it appeared in an early issue of Air Enthusiast but am not 100% sure.
 

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Cy-27

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Jos's layout fits in with the cabin configuration in the DH document.
 

Cy-27

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More on the DH.126 from same de Havilland DH.126 (Additional Information) document (mentioned in my earlier post) from July 1960 ……

The DH.126 shared a number of common features with the DH.125 executive business jet.

Both aircraft shared the same basic layout including:
· Rear mounted engines
· High set tail plane
· Clean wing with large chord double slotted flaps

A great deal of the aerodynamic, aero elastic and structural problems were already known from the DH.125 programme. It was believed these would offered no unpleasant surprises in the DH.126. This was considered by de Havilland’s to have a favourable influence on development time and costs.

The flight deck and controls, instrumentation seats radio and radar would be common between the two designs.

The various ancillary services, as well as the pressurised cabin equipment, would also be common to a large extent.
All of the above features would, in addition to having a beneficial effect on development time and cost, would also lower the final production costs.

Despite the economics expressed above, the document also quotes costs for a production run of 200 aircraft. The document had a development total of £2,707,500 and basic selling price £140,000 per unit.

Also attached are a series of scans showing:

· Comparison payload and range characteristics of the Avro 748 Series 2, DH.123, DC-3 and DH.126.
· DH.126 payload and range at cruise speeds
· Comparison bar graphs for the DH.123, DC-3 and DH.126.
· A statement showing the various engine options together with costs.
 

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Cy-27

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Finally, the military configurations layouts for the electronic and navigational training versions of the DH.126.

Envisaged to replace the Vickers Varsity and Valetta.
 

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  • DH126_Military_Trainer_Config_Drawing.jpg
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